I have some questions about this:

1.- What are the proper "partition_size_nominal" and "uncompressed_tarball_size" values for boot and root partitions of the latest release of Ubuntu MATE? or Where do I get those values?

2.- Does any of these values indicate the OS partition size on my SD card?

So... Is there any way for install Ubuntu MATE on NOOBS multiboot on a Raspberry Pi 3? NoobS allows one to add an OS not included, it is somewhere in the ReadMe: https://github.com/raspberrypi/noobs/blob/master/README.md You mean "How to create a custom OS version" section, right? But it doesnt wor...

So... Is there any way for install Ubuntu MATE on NOOBS multiboot on a Raspberry Pi 3?